Abstract: Early perforation failure of a drill pipe occurred in the process of using in the oil field. The macroscopic morphology, chemical composition, microstructure, mechanical properties and hardness of the failed drill pipe were analyzed by physical and chemical testing technology. The results show that under the action of corrosive medium in the process of drilling, a corrosion pit forms at the pricking point of inner wall of the drill pipe. Under the action of complex alternating stress load, microcracks form at the bottom of the corrosion pit on the surface of the drill pipe and propagates rapidly, resulting in the corrosion fatigue failure of the drill pipe. In order to prevent this kind of failure, it is necessary to strictly control the steel pipe rolling process, select the appropriate rolling tool size, improve the surface quality of the inner and outer walls of the steel pipe, and avoid the corrosion fatigue failure of the drill pipe used in the oil field.

Key words: drill pipe, pricking, corrosion pit, crack, corrosion fatigue